The rationale of this project is to develop a method to monitor the expression levels of a large number of genes in various experimental conditions and to understand global changes of gene expression patterns in development and aging. The systematic analysis of expression patterns of a large number of genes is rapidly becoming the method of choice for many laboratories to understand biological systems. Accordingly, the demand for high quality cDNA libraries and cDNA microarrays is increasing. The goals of this research project are to collect mouse cDNA clones and prepare cDNA microarrays containing as many mouse genes as possible. During this period, we have assembled a 15,000 unique gene set from mouse, which consists of 2132 genes from E7.5 extraembryonic tissue cDNA library, 893 genes from E7.5 embryonic tissue cDNA library, 7692 genes from preimplantation cDNA libraries (unfertilized eggs, fertilized eggs, 2-cell, 4-cell, 8-cell, 16-cell embryos and blastocysts), and 4620 genes from E12.5 mesonephros and newborn ovary cDNA libraries. These cDNA clones were resequenced to verify clone identities and to recover more sequence information from individual cDNA clones. This "NIA Mouse 15K cDNA Clone Set" has been freely distributed to the scientific community for cDNA microarray work and other fundamental research. An additional 60,000 ESTs from various mouse organs/tissues and stem cells have also been generated and assembled into a supplementary 7.4K set, which has also been freely distributed to the research community. We have recently developed a method to isolate long-insert cDNA clones more efficiently from submicrogram quantities of total RNA. Future libraries will be made by this method. Future plans include the expansion of the set of unique genes by sequencing more cDNA clones from various embryonic collections, and the preparation and use of cDNA microarrays from the expanded set of unique genes.